Sintered alloy having wear resistance at high temperature comprising fe-mo-c alloy skeleton infiltrated with cu or pb base alloys,sb,cu,or pb

ABSTRACT

THE PRESENT INVENTION RELATES TO IRON-BASE SINTERED ALLOYS HAVING EXCELLENT WEAR RESISTANCE AT HIGH TEMPERATURE, AND MORE PARTICULARLY TO ALLOYS ADAPTED FOR FABRICATING VALVE SEAT RINGS OF INTERNAL COMBUSTION ENGINES. THE ALLOYS COMPRISE METALS HAVING LUBRICATING PROPERTIES OR ALLOYS THEROF INFILTRATED INTO PORES OF IRON-BASE SINTERED ALLOYS HAVING HIGH STRENGTH AND WEAR RESISTANCE AT HIGH TEMPERATURE.

United States Patent Claims priority, application Japan, June 28, 1971,46/46,995 Int. Cl. B22f 5/00 US. Cl. 29182.1 36 Claims ABSTRACT OF THEDISCLOSURE The present invention relates to iron-base sintered alloyshaving excellent wear resistance at high temperature, and moreparticularly to alloys adapted for fabricating valve seat rings ofinternal combustion engines. The alloys comprise metals havinglubricating properties or alloys thereof infiltrated into pores ofiron-base sintered alloys having high strength and wear resistance athigh temperature;

BACKGROUND OF THE INVENTION The present invention relates to sinteredalloys resistant to wear at high temperatures.

Materials such as special cast iron and heat resistant steel haveusually been employed for valve seat rings of internal combustionengines. These materials are excellent when leaded gasoline is used asfuel since lead oxide formed from lead tetrachloride of antiknock agentsofiers lubricating action through its attachment onto the surface ofvalve seat rings. This prevents the valve seat rings from wearing away,and also results in full performance of the engine, However, thesematerials have the disadvantage that lubricating action by lead oxide islost and the wearing away of the valve seat rings is thereby remarkablyincreased when LPG (liquefied propane gas) or lead-free gasoline is usedas fuel. The engine suffers from the decreased output and abnormaloperation.

The above mentioned disadvantage is overcome by using the alloys of thepresent invention. The valve seat rings made of the alloys of thepresent invention have excellent resistance to Wear even when LPG orlead-free gasoline is used as fuel. Moreover, the engine is maintainedat a normal working condition. Also, the alloys of the present inventionmay be used to fabricate bearings for hot rollers or other parts thatare exposed to or may reach high temperatures.

SUMMARY OF THE INVENTION The present invention relates to sinterediron-base alloys obtained by infiltrating types of metals or alloysthereof having lubricating action into the pores of the sinterediron-base body. The sintered iron-base body available for this purposehas a specific composition in which iron is contained as the principalconstituent with 0.25 to 8 percent molybdenum, 0.1 to 1.0 percentcarbon, and 0.2 to 2.0 percent of one or two or more types selected fromtungsten, vanadium, titanium and tantalum, as the remainingconstituents. Also, iron is contained as the principal constituent with0.25 to 8 percent molybdenum, 0.1 to 1.0 percent carbon, and 1 to 20percent nickel and copper used alone or in combination, as theremainder. Further, iron is contained as the principal constituent with0.25 to 8 percent molybdenum, 0.1 to 1.0 percent carbon, and 0.1 to 2.0percent of one or two or more types selected from phosphorus, sulfur andboron, as the remainder. 0n the other hand, the metals and alloys3,806,325 Patented Apr. 23, 1974 ice thereof having lubricating actioninclude: copper or copper alloys mixed with one or two or more metalsselected from chromium, tin and zinc, which are used for infiltration by10 to 30 percent of the resulting sintered alloys; and copper-leadalloys, or copper-lead alloys added with one or two or more metalsselected from chromium, tin and zinc, which are for infiltration by 5 to30 percent of the resulting alloys; further lead, antimony or leadalloys added with one or two or more metals selected from bismuth,antimony and cadmium, which are used for infiltration by 1 to 25 percentof the resulting alloys. The percentages shown above and hereinafter aregiven by way of weight percent.

DETAILED DESCRIPTION OF THE INVENTION The sintered alloys according tothe present invention are characterized by infiltrating molten metals oralloys thereof having a lubricating action into the pores of thesintered ironbase body having high strength and Wear resistance at hightemperature. These alloys are particularly suitable for valve seat ringconstructions of internal combustion engines.

The effect of each constituent element and the reason for defining thepercentage of each element are given below. First, description is madewith reference to each element to be added to the sintered iron-basebody (or the sintered skeleton).

Carbon permeates into iron in the form of a solid solution and formspearlite thereby increasing the wear resistance as well as strengtheningthe alloys. But, at less than 0.1% carbon content, such effect isinappreciable. On the other hand, addition of more than 1.0% carbonresults in precipitating cementite which renders the alloys fragile andalso deteriorates the machinability of the alloys. Therefore, thepercentage of carbon desired is between 0.1% and 1.0%.

Addition of molybdenum increases the resistance against softening of thealloys by temper, and their impact value as well. Moreover, molybdenum,as precipitated and pseudoprecipitated, forms an oxide at hightemperature thereby lowering the coefficient of friction and raising thewear resistance. No substantial effect of such kind, however, isobserved at less than 0.25% content, and by adding more than 8% theeffect is not increased. Accord-.

ingly, the desirable range of molybdenum is between 0.25% and 8%.

Tungsten, vanadium, titanium or tantalum, when added sulting alloysfragile and difiicult to machine. However,

addition of less than 0.2% of these elements does not appreciablyincrease the strength and wear resistance of the alloys. Therefore, therange should preferably be between 1 0.2% and 2.0%.

Nickel permeates into iron in the form of a solid solu-: tion andincreases the mechanical strength and heat re-- sistance of theresulting alloys.

Copper added to the sintered skeletons permeates, in part, into iron inthe form of a solid solution and in-. creases the hardness andmechanical strength of the resulting alloys. The other part of thecopper remains in. the pores of the sintered skeletons and takes thesame.

action as that of copper used for infiltration.

When added simultaneous, the above mentioned effect is also givenrespectively by nickel and copper. However,

at less than 1% of these elements the effect is little, and

at more than 20% the hardness of the resulting alloys increasesexcessively and the machinability is adversely affected. Therefore, therange is desirably between 1% and 20%.

Phosphorus or sulfur, when added to the sintered skeletons, improves themachinability and lowers the coefiicient of friction thereby increasingthe wear resistance. Further, the mechanical properties of the alloysare improved by addition of these elements up to 2%. At more than 2%,however, the fragility advances unsatisfactorily. To the contrary,addition of less than 0.1% will not bring appreciable effect.

Boron increases the hardness and the tensile strength and remarkablyimproves the wear resistance. However, at less than 0.2% its effect isslight, and the impact value sharply drops at more than 1%. Therefore,the range of 0.2 to 1.0% is preferable.

Next, a description is made with reference to the infiltratingmaterials. Part of the copper permeates into iron in the form of a solidsolution thereby increasing the hardness and strengthening the alloys aswell as i11- creasing the wear resistance. The remaining copper fillsthe pores of the sintered skeletons thereby increasing the heatconductivity which in turn reduces the heat load by the alloy materials.At the same time, copper forms a thin oxide film on the surface at hightemperature which produces a lubricating effect thereby improving thewear resistance of the resultant alloys. However, at less than 10%copper the effect is slight, and at more than 30% the density of thesintered skeletons and the strength of the alloys diminish. Therefore,the desirable range of copper used for infiltration is between 10 and30% As for chromium which is added to copper for infiltration, part ofit permeates into copper in the form of a solid solution therebystrengthening the copper and at the same time preventing the alloys fromadhering by melt onto the part which contacts them in use. Abrasionowing to this action is significantly decreased. The remaining part ofthe chromium disperses into copper and forms a thin oxide film on thesurface of the alloys at high temperature which lowers the coeificientof friction thereby increasing the wear resistance.

Lead, used in Example 5 as one of the infiltrating materials, asexplained below, is thinly coated onto the contacting surface of thealloys at high temperature and forms lead oxide which promotes thelubricating action thereby increasing the 'wear resistance. However, atless than 1% its effect is insufiicient and at more than 25% it is notuseful in strengthening the sintered skeletons.

Cadmium, as added to lead, affects restraining lead from expansion whenmelting whereby lead may be more captured.

Further-more, as shown in Example 3 below, where 70% copper-30% leadalloys (Kelmet) are infiltrated, namely, copper and lead aresimultaneously infiltrated, copper improves the wettability of leadtoward the iron matrix thereby more uniformly and thinly attaching leadonto the contacting surface of the alloys than in the case ofinfiltrating with lead alone. This also increases the lubricating actionby lead oxide. The simultaneous effect of copper and lead is in additionto the above noted individual influences of each of these metals. Tin,as infiltrated simultaneously with copper, strengthens the copper matrixand increases the wear resistance. Zinc has a similar effect to tin. InExample 4 below, tin is used for infiltartion together with copper andlead. Tin contributes to a fine and uniform dispersion of lead incopper.

Antimony has an affect similar to lead, and is particularly suitable forapplication cases using high temperature since the melting point ofantimony (630 C.) is higher when compared with the melting point of lead(327 C.). The content of antimony is preferably between 1 and 25%because its effect is slight at less than 1% and the resulting alloystend to lack strength at more than 25%.

In Example 6 where 80% lead and 20% bismuth are infiltrated, the bismuthis suitable for cases where low temperature is employed because additionof bismuth to lead lowers the melting tendency of lead. Further, inExample 8 where a lead-antimony alloy for infiltration is shown, thiscombination is suitable for the cases where relatively high temperatureis employed because addition of antimony by about 25 or more to leadelevates the melting tendency of lead. (e.g. about 520 C. at 60%antimony content).

As described above, the sintered alloys according to the presentinvention comprise, at first, providing iron molybdenum-carbon sinteredskeletons with improved strength and wear resistance at high temperaturethrough addition of (l) vanadium, titanium or tantalum which formscarbides such as WC, VC, TiC or TaC dispersed in the alloys; (2) nickelor copper which permeates into the alloys in the form of a solidsolution to strengthen the alloys; (3) phosphorous of sulfur which hasthe lubricating action; or (4) boron which has wear resistance at hightemperature. Secondly, the resulting alloys are provided with greatlyincreased wear resistance at high temperature by infiltrating the poresof the sintered skeletons with soft metals or alloys thereof havinglubricating action, specifically, copper or copper alloys added with oneor two or more metals selected from chromium, tin and zinc; copper-leadalloys or copper-lead alloys added with one or two or more metalsselected from chromium, tin and zinc; lead or antimony, or lead alloysadded with one or two or more metals selected from bismuth, antimony andcadmium. Thus, because of their excellent properties, these alloys aremost suitable for materials in valve seat rings of internal combustionengines and in bearings which may reach or be exposed to hightemperature.

The present invention will be described in detail with reference to itsvarious embodiments as noted below:

EXAMPLE 1 Reducing iron powder of minus 100 mesh, fine electrolyticmolybdenum powder of 3 to 6 in particle size, graphite powder andiron-tungsten alloy powder of minus 200 mesh and mixed to provide acomposition of 92.4% iron, 5% molybdenum, 2% tungsten and 0.6% carbon.The mixture is formed under a forming pressure of 5 t./cm. to a densityof 6.7 g./crn. After the formed mass is subjected to a sintering processat 1170 C. for one hour and a half in a reducing gas atmosphere, asintered skeleton is obtained.

Thereafter, the sintered skeleton is infiltrated with copper using aninfiltrating material composed of cop per, 5% iron and 5% manganese at1130" C. for one hour and a half in a reducing gas atmosphere. Asintered alloy of the present invention is obtained.

EXAMPLE 2 Reducing iron powder of minus 100 mesh, fine electrolyticmolybdenum powder of 3 to 6; in size, graphite powder and iron-titaniumalloy powder of minus 200 mesh are mixed to provide a composition of92.2% iron, 5% molybdenum, 2% titanium and 0.8% carbon. The mixture isthen formed under a forming pressure of 5 t./cm. to a density of 6.7g./cm. Thereafter, the formed mass is subjected to a sintering processat 1170 C. for one hour and a half in a non-oxidizing gas atmosphere andthus a sintered skeleton is obtained. After the sintered skeleton isinfiltrated using copper-5% chromium alloy at 1130 C. for one hour and ahalf in a nonoxidizing gas atmosphere, a sintered alloy of the presentinvention is obtained.

EXAMPLE 3 Reducing iron powder of minus mesh, fine electrolyticmolybdenum powder of 3 to 6 in size, graphite powder and iron-vanadiumalloy powder (30% iron and 70% vanadium) of minus 100 mesh are blendedto provide a composition of 92.2% iron, 5% molybdenum, 2% vanadium and0.8% carbon. After the mixture is formed under a forming pressure of 5t./cm. to a density of 6.7 g./cm. the formed mass is subjected to asintering process at 1170 C. for one hour and a half in a reducing gasatmosphere. A sintered skeleton is obtained. The pores of the sinteredskeleton are infiltrated with a 70% copper-30% lead alloy (Kelmet) at1050 C. for one hour in a reducing gas atmosphere. A sintered alloy ofthe present invention is obtained.

EXAMPLE 4 Reducing iron powder of minus 100 mesh, fine electrdlyticmolybdenum powder of 3 to 6p. in size, graphite powder and tantalummilled powder of minus 100 mesh are blended to provide a composition of92.9% iron, 5% molybdenum, 1.5% tantalum and 06% carbon. After themixture is formed under a forming pressure of 5 t./cm. to a density of6.7 g./cm. the formed mass is subjected to a sintering process at 1170C. for one hour and a half in a reducing gas atmosphere. A sinteredskeleton is obtained. The pores of this sintered skeleton areinfiltrated with a 60% copper-30% lead-10% tin alloy at 1050 C. for onehour, and a sintered alloy of the present invention is obtained.

EXAMPLE 5 Reducing iron powder of minus 100 mesh, fine electrolyticmolybdenum powder of 3 to 6p. in size, graphite powder and fine carbonylnickel powder of about 4 in average size are mixed together to provide acomposition of 89.7% iron, 5% molybdenum, 5% nickel and 0.3% carbon.This mixture is then formed under a forming pressure of 5 t./cm. to adensity of 6.7 g./cm. After the formed mass is subjected to a sinteringprocess at 1170 C. for one hour and a half in a reducing gas atmosphere,a sintered skeleton is obtained. The sintered g./cm. To obtain asintered skeleton, the formed mass is subjected to a sintering processat 1130 C. for one hour and a half in a reducing gas atmosphere.Thereafter, the pores of the sintered skeleton are infiltrated withantimony at 1100 C. for one hour in a reducing gas atmosphere. Asintered alloy of the present invention is obtained.

EXAMPLE 8 Reducing iron powder of minus 100 mesh, fine electrolyticmolybdenum powder, graphite powder and ironphosphorus alloy powder ofminus 100 mesh are mixed to provide a composition of 94.1% iron, 5%molybdenum, 0.3% phosphorus and 0.6% carbon. The mixture is then formedunder a forming pressure of 6 t./cm. to a density of 7.1 g./cm. Theformed mass is subjected to a sintering process at 1130 C. for one hourand a half in a reducing gas atmosphere and a sintered skeleton isobtained. The pores of the sintered skeleton are infiltrated with alead-60% antimony alloy at 1050 C. for one hour, and a sintered alloy ofthe present invention is obtained.

Moreover, the alloys of the present invention as obtained in Examples 1through 8 are tested for their properties and quantities of wear at hightemperature. The results are shown in the following table. In the table,quantities of wear are indicated by the worn away quantities inmillimeters in the direction of the height of the specimens measuredafter the testing has been continued for 100 hours by a so-calledsliding high-cycle impact tester, wherein 2500 shocks a minute are givento the angular specimens under a surface pressure of 30 kg./cm. by meansof a jig made of heat resistant steel, while the angular specimens fixedto cast iron are rotated 10 times a minute at an elevated temperature of500 to 550 C.

TABLE Composition (percent by weight) skeleton is then infiltrated withlead at 1000 C. for minutes in a reducing gas atmosphere. A sinteredalloy of the present invention is obtained.

EXAMPLE 6 Reducing iron powder of minus 100 mesh, fine electrolyticmolybdenum powder, graphite powder and electrolytic copper powder ofminus 100 mesh are mixed to provide a composition of 87.7% iron, 5%molybdenum, 7% copper and 0.3% carbon. The mixture is then formed undera forming pressure of 5 t./cm. to a density of 6.7 g./cm. Thereafter,the formed mass is subjected to a sintering process at 1150 C. for onehour and a half in a reducing gas atmosphere. The pores of the resultingsintered skeleton are infiltrated with 80% lead-20% bismuth alloy at1000 C. for 45 minutes in a reducing gas atmosphere. A sintered alloy ofthe present invention is obtained.

EXAMPLE 7 Reducing iron powder of minus 100 mesh, fine electrolyticmolybdenum powder of 3 to 6p. in size, graphite powder and sulfur powderfor chemical use are mixed to provide a composition of 93.2% iron, 5%molybdenum, 1% sulfur and 0.8% carbon. The mixture is then formed undera forming pressure of 6 t./cm. to a density of 7.1

--. (Fe-5Mo-2W-0.6C)-14Gu infiltrated (Fe-5Mo-2Ti-0.8C)-14(Cu-5 Cr)infiltrated (Fe5M0-0.3P-0.6C)-9(Pb-60Sb) infiltratedFe-3.5C-2.5Si-1Mn-0.5P-1.5Cr-0.5Mo-0.1V Fe-O.40-2Sl-15Cr-15Ni-2W-0.5Mn

What is claimed is:

1. A wear resistant metal comprising a sintered skeleton consistingessentially of iron having 0.25 to 8 percent by weight molybdenum, 0.1to 1.0 percent by weight carbon, and 0.2 to 2.0 percent by weight atleast one metal selected from the group consisting of tungsten,vanadium, titanium and tantalum, and an infiltrant selected from thegroup consisting of 10 to 30 percent by weight copper, 10 to 30 percentby weight copper-base alloy, 1 to 25 percent by weight lead, 1 to 25percent by weight lead-base alloy, and 1 to 25 percent by weightantimony.

2. A valve seat for an internal combustion engine fabricated of the wearresistant metal of claim 1.

3. The wear resistant metal of claim 1 in which the copper-base alloyinfiltrant includes at least one metal selected from the groupconsisting of chromium, tin and 4. A valve seat for an internalcombustion engine fabricated of the wear resistant metal of claim 3.

5. A wear resistant metal of claim 25 in which the copper-lead basealloy infiltrant includes at least one metal selected from the groupconsisting of chromium, tin and 6. A valve seat for an internalcombustion engine fabricated of the wear resistant metal of claim 5.

7. The wear resistant metal of claim 1 in which the lead-base alloyinfiltrant includes at least one metal selected from the groupconsisting of bismuth, antimony and cadmium.

8. A valve seat for an internal combustion engine fabricated of the wearresistant metal of claim 7.

9. A wear resistant metal comprising a sintered skeleton consistingessentially of iron having 0.25 to 8 percent by weight molybdenum, 0.1to 1.0 percent by weight carbon, and 1 to 20 percent by weight at leastone metal selected from the group consisting of nickel and copper, andan infiltrant selected from the group consisting of to 30 percent byweight copper, 10 to 30 percent by weight copper-base alloy, 1 to 25percent by weight lead, 1 to 25 percent by weight lead-base alloy, and 1to 25 percent by weight antimony.

10. A valve seat for an internal combustion engine fabricated of thewear resistant metal of claim 9.

11. The wear resistant metal of claim 9 in which the copper-base alloyinfiltrant includes at least one metal selected from the groupconsisting of chromium, tin and 21110.

12. A valve seat for an internal combustion engine fabricated of thewear resistant metal of claim 11.

13. The wear resistant metal of claim 29 in which the copper-lead basealloy infiltrant includes at least one metal selected from the groupconsisting of chromium, tin and zinc.

14. A valve seat for an internal combustion engine fabricated of thewear resistant metal of claim 13.

15. The wear resistant metal of claim 9 in which the lead-base alloyinfiltrant includes at least one metal selected from the groupconsisting of bismuth, antimony and cadmium.

16. A valve seat for an internal combustion engine fabricated of thewear resistant metal of claim 15.

17. A wear resistant metal comprising a sintered skeleton consistingessentially of iron having 0.25 to 8 percent by weight molybdenum, 0.1to 1.0 percent by weight carbon, and 0.1 to 2.0 percent by weight atleast one metal selected from the group consisting of phosphorous,sulfur and boron, and an infiltrant selected from the group consistingof 10 to 30 percent by weight copper, 10 to 30 percent by weightcopper-base alloy, 1 to 25 percent by weight lead, 1 to 25 percent byweight lead-base alloy, and 1 to 25 percent by weight antimony.

18. A valve seat for an internal combustion engine fabricated of thewear resistant metal of claim 17.

19'. The wear resistant metal of claim 17 in which the copper-base alloyinfiltrant includes at least one metal selected from the groupconsisting of chromium, tin and zinc.

20. A valve seat for an internal combustion engine fabricated of thewear resistant metal of claim 19.

21. The wear resistant metal of claim 33 in which the copper-lead basealloy infiltrant includes at least one metal selected from the groupconsisting of chromium, tin and zinc.

22. A valve seat for an internal combustion engine fabricated of thewear resistant metal of claim 21.

23. The wear resistant metal of claim 17 in which the lead-base alloyinfiltrant includes at least one metal selected from the groupconsisting of bismuth, antimony and cadmium.

24. A valve seat for an internal combustion engine fabricated of thewear resistant metal of claim 23.

25. A wear resistant metal comprising a sintered skeleton consistingessentially of iron having 0.25 to 8 percent by weight molybdenum, 0.1to 1.0 percent by weight carbon, and 0.2 to 2.0 percent by weight atleast one metal selected from the group consisting of tungsten,vanadium, titanium and tantalum, and an infiltrant consisting of 5 to 30percent by weight copper-lead base alloy.

26. A valve seat for an internal combustion engine fabricated of thewear resistant metal of claim 25.

27. The wear resistant metal of claim 25 in which the copper-lead basealloy infiltrant comprisesS to 30 percent by weight copper-lead alloy.

28. A valve seat for an internal combustion engine fabricated of thewear resistant metal of claim 27.

29. A wear resistant metal comprising a sintered skeleton consistingessentially of iron having 0.25 to 8 percent by weight molybdenum, 0.1to 1.0 percent by weight carbon, and 1 to 20 percent by weight at leastone metal selected from the group consisting of nickel and copper, andan infiltrant consisting of 5 to 30 percent by weight copper-lead basealloy.

30. A valve seat for an internal combustion engine fabricated of thewear resistant metal of claim 29.

31. The wear resistant metal of claim 29 in which the copper-lead basealloy infiltrant comprises 5 to 30' percent by weight copper-lead alloy.

32. A valve seat for an internal combustion engine fabricated of thewear resistant metal of claim 31.

33. A wear resistant metal comprising a sintered skeleton consistingessentially of iron having 0.25 to 8 percent by Weight molybdenum, 0.1to 1.0 percent by weight carbon, and 0.1 to 2.0 percent by weight atleast one metal selected from the group consisting of phosphorous,sulfur and boron, and an infiltrant consisting of 5 to 30 percent byweight copper-lead base alloy.

34. A valve seat for an internal combustion engine fabricated of thewear resistant metal of claim 33.

35. The wear resistant metal of claim 33 in which the copper-lead basealloy infiltrant comprises 5 to 30 percent by weight copper-lead alloy.

36. A valve seat for an internal combustion engine fabricated of thewear resistant metal of claim 35.

References Cited UNITED STATES PATENTS 3,495,957 2/1970 Matoba et al.29--182.1 3,694,173 9/1972 Farmer et a1 29-182.1 2,753,859 7/1956Bartlett 29-182.1 X

CARL D. QUARFORTH, Primary Examiner R. E. SCHAFER, Assistant ExaminerU.S. Cl. X.R. -200

